This invention relates to a flexible disk in which a magnetic recording medium for recording and reproducing data is enclosed within a jacket.
A flexible disk of the type comprises a generally disk-shaped sheet-like magnetic recording medium and a jacket enclosing the magnetic recording medium so that the magnetic recording medium is rotatable. The magnetic recording medium comprises a flexible sheet made of synthetic resin or the like. A magnetic recording layer is formed on a surface of the sheet and a coating layer is formed on the magnetic recording layer. The magnetic recording medium is attached to a hub which makes the magnetic recording medium rotatable. In order to record or reproduce data in and from the flexible disk, the flexible disk is loaded in a disk drive. The disk drive comprises a rotation driving mechanism for rotating the magnetic recording medium, and a magnetic head for access to the magnetic recording medium being rotated. In the disk drive, the magnetic head is moved in a radial direction of the magnetic recording medium with respect to the magnetic recording medium being rotated and is brought into sliding contact with the surface of the magnetic recording medium. Through the magnetic head, data is written in the magnetic recording medium and data recorded in the magnetic recording medium is read from the magnetic recording medium.
In the flexible disk of the type, it is required to form an opening in the jacket in order to bring the magnetic head into sliding contact with the surface of the magnetic recording medium. In addition, another opening is required to expose the hub on an outer surface of the jacket. Therefore, the magnetic recording medium can not be sealed within the jacket. This implies that, when the flexible disk is reserved or used, dust readily enters through the openings into the jacket to be adhered onto the magnetic recording medium. Such dust sometimes makes it impossible for the magnetic head to normally read or write data from or into the magnetic recording medium. In other words, if dust is adhered onto the magnetic recording medium, an error may occur in access by the magnetic head.
With a demand for an increase in memory capacity, development has been made of a flexible disk having a very large memory capacity as compared with that having a normal memory capacity. For example, the normal memory capacity is on the order between 1 M and 2 Mbytes. In contrast, a flexible disk having a memory capacity on the order between 100 and 130 Mbytes has been recently put into practical use. In case of the flexible disk having such a large capacity, a reading error or a writing error due to the presence of dust tends to occur. tends to occur.